Question

我编写了RetrieveUrl类来从URL获取JSON数据。这一切都按预期工作，我可以看到一个闭包中的数据变量返回一个值。但我想在MasterViewController.swift中的一个表中显示这些数据尝试了几件事，但似乎我对Swift闭包的知识非常有限。

import Foundation

class RetrieveUrl {

func httpGet(request: NSURLRequest!, callback: (String, String?) -> Void)                   
{
    var session = NSURLSession.sharedSession()
    var task = session.dataTaskWithRequest(request){
        (data, response, error) -> Void in
        if error != nil {
            callback("", error.localizedDescription)
        } else {
            var result = NSString(data: data, encoding:
                NSASCIIStringEncoding)!
            callback(result, nil)
        }
    }
    task.resume()

}

func makeRequest() -> () {

    var request = NSMutableURLRequest(URL: NSURL(string: "http://someapi_url")!)

    var result:String = ""

    httpGet(request){
        (data, error) -> Void in
        if error != nil {
            result = error!
        } else {
            result = data
        }
    }

   }
}

我要显示此数据的MasterViewController.swift代码

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
    let object = objects[indexPath.row] as NSDate

    // Showing data from URL
    var getUrlObject = RetrieveUrl()
    getUrlObject.makeRequest()

    cell.textLabel!.text = object.description

    return cell
}

Answer 1

更新的代码： class RetrieveUrl {

func httpGet(request: NSURLRequest!, callback: (NSString, NSString?) -> Void)
{
    var session = NSURLSession.sharedSession()
    var task = session.dataTaskWithRequest(request){
        (data, response, error) -> Void in
        if error != nil {
            callback("", error.localizedDescription)
        } else {
            var result = NSString(data: data, encoding:
                NSASCIIStringEncoding)!
            callback(result, nil)
        }
    }
    task.resume()

}

func makeRequest(callback: (NSString) ->Void) -> Void {

    var request = NSMutableURLRequest(URL: NSURL(string: "http://sample_url")!)

     var result:NSString = ""


    httpGet(request){
        (data, error) ->  Void in

        if error != nil {
            result = error!
        } else {
            result = data
        }


        callback(data)
    }

}

}

用法：

    let retrieveObj = RetrieveUrl()
     retrieveObj.makeRequest(){
         (data) ->  Void in
        println("response data:\(data)")

    }

}

如何从Swift中的闭包中获取数据

1 个答案: